METHODS FOR SOIL MICROBIAL BIOMASS ASSESSMENT:THEIR PRINCIPLES, APPLICABILITY AND FUTURE TRENDS

Abstract

The soil microbial biomass is of paramount importance for the understanding of the organic matter combover, nutrient cycling and energy flux in the soil. The most widespread and correlated methods are direct microscopy for fluorescent stained microorganisms (Biovolume), the chemical methods (ATP=adenosine triphosphate and fumigation-extraction—FE), and the physiological methods (fumigation-incubation=FI and substrate induced respiration—SIR). The biovolume method is rather subjective and time consuming, while the chemical and physiological methods are of better reproducibility and applied to a wider range of soils. For lowland soils, the methods tested are basically the same as for upland soils. The data available show that the FE and modified versions of Fl and SIR have a satisfactory performance, but the original ATP method seems to be unsuitable. The expression usually found in the literature does not refer to the total microbial biomass, but rather to specific components of the biomass I like C, N and ninhydrin reactive nitrogen. For the forthcoming years, significant increase in research is expected involving ATP, SIR, Fl and FE methods in organic matter turnover and energy cycling. The flourishing methods for biomass assessment of particular groups of microorganisms as well as the molecular techniques for the identification of individual components of the biomass are also expected to become more popular.